According to ancient Egyptian manuscripts, the eye makeup was believed to have a magical role, in which the gods Horus and Ra would protect wearers against several illnesses.

Bacterial eye infections such as conjunctivitus, for example, would have been a common problem along the Nile's tropical marshes.

But previous chemical analyses of powder residue, taken from ancient makeup containers, had isolated four lead-based compounds.

That would seem to suggest that the makeup was harmful, since lead can be highly toxic to humans.

Makeup's "Magic" Required Hard Work

Instead, the new study found that the low doses of lead salts in the makeup may have actually had beneficial properties: When the salts come into contact with skin, they boost the body's production of nitric oxide.

This chemical is known to stimulate the immune system and help fight off disease-causing bacteria.

Based on the amount of the lead compounds in the ancient makeup, a wearer's nitric oxide levels would have increased by 240 percent, the study found.

"Two of these chemicals do not occur naturally, and would have taken 30 days of hard work to make," Amatore said.

"In my opinion, [the ancient Egyptians] were aware that these compounds brought good health, and they were making them on purpose."